Colour conversion film, and back light unit and display device comprising same

ABSTRACT

A color conversion film having:
         a substrate film, a color conversion layer provided on the substrate film and   a phase transformation adhesive layer including an adhesive resin matrix and a phase change material, and a backlight unit and a display apparatus including the color conversion film.

The application is a 35 U.S.C. 371 National Phase Entry Application fromPCT/KR2019/015238 filed on Nov. 11, 2019, designating the United States,which claims priority to and the benefits of Korean Patent ApplicationNo. 10-2018-0138417, filed with the Korean Intellectual Property Officeon Nov. 12, 2018, the entire contents of which are incorporated hereinby reference.

The present specification relates to a color conversion film, and abacklight unit and a display apparatus including the same.

BACKGROUND ART

Development of a color conversion film using various materials has beenprogressed recently for improving color gamut of LCD displays such asTVs.

A color conversion film generally has a problem of reducing durabilityby accelerating degradation due to heat, oxygen or the like togetherwith light. Accordingly, there have been demands for material selectionand structure improvements capable of reducing their effects.

Particularly, enhancing heat resistance properties is essential in acolor conversion film due to its inevitable exposure to the heat of abacklight and the like generated during display driving.

There have been attempts in the art to enhance thermal stability throughsubstituting a functional group of a fluorescent substance, introducinga resin with high heat resistance, and the like, however, enhancing heatresistance has been limited since heat transfer to a color conversionlayer itself has not been prevented. Accordingly, new technologiescapable of preventing film degradation caused by heat have beenrequired.

BRIEF DESCRIPTION OF THE INVENTION

The present specification provides a color conversion film, and abacklight unit and a display apparatus including the same.

One embodiment of the present specification provides a color conversionfilm including a substrate film; a color conversion layer provided onthe substrate film; and a phase transformation adhesive layer providedon the color conversion layer, wherein the phase transformation adhesivelayer includes an adhesive resin matrix and a phase change material, andthe phase change material is at least one selected from the groupconsisting of an organic monomer, a polymer and an inorganic salthydrate.

Another embodiment of the present specification provides a method forpreparing a color conversion film, the method including preparing asubstrate film; forming a color conversion layer on the substrate film;and forming a phase transformation adhesive layer including an adhesiveresin matrix and a phase change material on the color conversion layer,wherein the phase change material is at least one selected from thegroup consisting of an organic monomer, a polymer and an inorganic salthydrate.

Another embodiment of the present specification provides a backlightunit including the color conversion film described above.

Another embodiment of the present specification provides a displayapparatus including the backlight unit described above.

ADVANTAGEOUS EFFECTS

In a color conversion film according to one embodiment of the presentspecification, heat generated during display driving is absorbed by aphase change material in a phase transformation adhesive layer, andtherefore, degradation of the color conversion film caused by heat canbe reduced.

In addition, the color conversion film according to one embodiment ofthe present specification includes a phase change material in a layerseparate from a color conversion layer, and therefore, changes in thevolume that may occur during the phase transition or leakage of thephase change material can be minimized.

[BRIEF DESCRIPTION OF DRAWINGS]

FIG. 1 is a mimetic diagram of a color conversion film according to oneembodiment of the present specification.

FIGS. 2 and 3 are mimetic diagrams illustrating structures of abacklight unit according to one embodiment of the present specification.

FIG. 4 is a mimetic diagram illustrating a structure of a displayapparatus according to one embodiment of the present specification.

FIG. 5 is a graph showing brightness spectra of a color conversion filmaccording to one embodiment of the present specification and a film of acomparative example.

FIG. 6 is a graph evaluating repeated driving durability of colorconversion films prepared according to an example and a comparativeexample according to one embodiment of the present specification.

Reference Numeral

10: Substrate Film

20: Color Conversion Layer

30: Phase Transformation Adhesive Layer

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present specification will be described in more detail.

In the present specification, a description of one member being placed“on” another member includes not only a case of the one member being incontact with the another member but a case of still another member beingpresent between the two members.

In the present specification, a description of a certain part“including” certain constituents means capable of further includingother constituents, and does not exclude other constituents unlessparticularly stated on the contrary.

One embodiment of the present specification provides a color conversionfilm including a substrate film; a color conversion layer provided onthe substrate film; and a phase transformation adhesive layer providedon the color conversion layer, wherein the phase transformation adhesivelayer includes an adhesive resin matrix and a phase change material, andthe phase change material is at least one selected from the groupconsisting of an organic monomer, a polymer and an inorganic salthydrate.

The phase change material absorbs heat by causing a phase transition ina certain temperature range, and through such heat absorption, heattransfer to the color conversion layer may be prevented. Specifically,the phase change material may cause a solid-liquid phase transition at30° C. to 80° C. When a phase transition occurs at a temperature oflower than 30° C., an effect of stabilization obtained by heatabsorption may not be significant in a driving temperature range of thecolor conversion film, and when a phase transition occurs at atemperature of higher than 80° C., a heat absorbing ability of the phasechange material is reduced causing degradation by transferring much heatto the color conversion layer.

According to one embodiment of the present specification, the phasetransformation adhesive layer may be formed with a phase change materialand an adhesive material. The adhesive material is not particularlylimited as long as it may be commonly used in an adhesive layer.

According to one embodiment of the present specification, the content ofthe phase change material may be from 10 parts by weight to 80 parts byweight with respect to 100 parts by weight of the phase transformationadhesive layer. When introducing a content of less than 10 parts byweight, a heat absorbing ability of the phase transformation adhesivelayer is reduced resulting in an insignificant durability enhancingeffect, and when introducing a content of greater than 80 parts byweight, viscosity of the coating solution decreases decliningprocessability.

According to one embodiment of the present specification, the content ofthe phase change material may be greater than or equal to 5 parts byweight and less than or equal to 100 parts by weight with respect to 100parts by weight of the adhesive resin matrix. Specifically, the contentmay be 5 parts by weight or greater, 10 parts by weight or greater, 15parts by weight or greater, 20 parts by weight or greater, 25 parts byweight or greater, 30 parts by weight or greater, 35 parts by weight orgreater, 40 parts by weight or greater, 45 parts by weight or greater or50 parts by weight or greater, and may be 95 parts by weight or less, 90parts by weight or less, 85 parts by weight or less, 80 parts by weightor less, 75 parts by weight or less or 70 parts by weight or less.

According to one embodiment of the present specification, the phasechange material has a microcapsule structure, and the microcapsulestructure may include a shell and a core.

In addition, according to one embodiment of the present specification,the shell may be at least one selected from the group consisting ofurea-formaldehyde, melamine-formaldehyde, a polyurethane resin, apolyurea resin, an epoxy resin, gelatin and a polyacrylic resin, and thecore may be at least one selected from the group consisting of anorganic monomer, a polymer and an inorganic salt hydrate.

According to one embodiment of the present specification, the organicmonomer may be at least one selected from the group consisting of aparaffin-based compound, a fatty acid-based compound, an alcohol-basedcompound and a carbonate-based compound.

The paraffin-based compound is not particularly limited, but may be atleast one selected form the group consisting of n-nonadecane,n-eicosane, n-heneicosane, n-docosane, n-tricosane, n-tetracosane,n-pentacosane, n-hexacosane, n-heptacosane and n-octacosane.

The fatty acid-based compound is not particularly limited, but may be atleast one selected form the group consisting of capric acid, lauric acidand myristic acid.

The alcohol-based compound is not particularly limited, but may be atleast one selected form the group consisting of 1-dodecanol and1-tetradecanol.

The carbonate-based compound is not particularly limited, but may be atleast one selected form the group consisting of tetradecyl carbonate,hexadecyl carbonate and octadecyl carbonate.

According to one embodiment of the present specification, the polymermay be at least one selected form the group consisting of poly(ethyleneglycol), poly(propylene oxide) (PPO) and polytetrahydrofuran (PTHF).

According to one embodiment of the present specification, the inorganicsalt hydrate may be at least one selected form the group consisting ofLiNO₃.3H₂O, Na₂SO₄.10H₂O, NaCH₃COO.3H₂O, CaBr₂.6H₂O, Na₂HPO₄. 12H₂O,Zn(NO₃)₂.nH₂O, Na₂S₂O₃.5H₂O and Cd(NO₃)₂.4H₂O.

In one embodiment of the present specification, as components formingthe adhesive resin matrix, adhesive components known in the art may beused. For example, the adhesive resin matrix may be a cationpolymerizable adhesive component, a radical curable adhesive component,or a mixture thereof.

In one embodiment of the present specification, the adhesive resinmatrix includes a cation polymerizable adhesive component.

The cation polymerizable adhesive component includes an adhesivecomponent cured by a cation polymerization reaction, and may be formedusing cation polymerizable compositions known in the art.

In one embodiment of the present specification, the cation polymerizablecomposition includes a cationic photopolymerization initiator. Thecationic photopolymerization initiator is a compound producing cationspecies or Lewis acids by active energy ray irradiation, and examplesthereof may include, but are not limited to, aromatic diazonium salts,aromatic iodine aluminum salts, onium salts such as aromatic sulfoniumsalts, iron-arene complexes and the like.

Components other than the cationic photopolymerization initiator in thecation polymerizable composition are not particularly limited. Forexample, in the cation polymerizable composition, a cation polymerizablecompound such as an epoxy compound, and, as necessary, a binder resin, areactive resin, additives and the like may be further used. For example,the cation polymerizable composition includes, based on 100 parts byweight of the composition, the cation polymerizable compound (forexample, epoxy compound) in 5 parts by weight to 90 parts by weight; andthe cationic photopolymerization initiator in 0.5 parts by weight to 20parts by weight, and as necessary, may further include additives formaintaining viscosity or for enhancing wetting.

In one embodiment of the present specification, the cation polymerizablecomposition may include a resin, a cationic photoinitiator and atackifier. As the resin, rubber-based resins may be used. The content ofthe cationic photopolymerization initiator may be determined asnecessary, and for example, may be from 30 parts by weight to 100 partsby weight with respect to 100 parts by weight of the resin. Thetackifier may be included in 30 parts by weight to 40 parts by weightwith respect to 100 parts by weight of the resin. In addition, additivesknown in the art may be further added as necessary.

In one embodiment of the present specification, the cation polymerizableadhesive component preferably does not include materials additionallygenerating radicals during UV irradiation.

In one embodiment of the present specification, the adhesive colorconversion layer may be formed by coating a cation polymerizablecomposition; and an organic fluorescent substance on a substrate, andcation polymerizing the result.

In one embodiment of the present specification, the adhesive resinmatrix includes a radical curable adhesive component. The radicalcurable adhesive component includes an adhesive component cured byradical curing, and may be formed using a radical curable compositionknown in the art The radical curable composition includes a radicalpolymerizable compound and a radical initiator, and as necessary, mayfurther include a rubber-based gluing resin and the like. Thecomposition may include a solvent as necessary, however, a separatesolvent may not be used when the composition including a radicalpolymerizable compound and a radical initiator is in a solution state.

The radical polymerizable compound is a compound polymerized through aradical polymerization reaction, and may use a radical polymerizablemonomer or polymer. As the radical polymerizable compound,polyisocyanate having two or more isocyanate groups in the molecule,urethane acrylate reacting hydroxyalkyl (meth)acrylate, (meth)acrylateshaving one or more (meth)acryloyl groups in the molecule,(meth)acrylamides, maleimides, (meth)acrylic acid, maleic acid, itaconicacid, (meth)acrylaldehyde, (meth)acryloylmorpholine,N-vinyl-2-pyrrolidone or triallyl isocyanurate and the like may be used.

The radical initiator may be used to facilitate polymerization of theradical polymerizable compound and enhance a curing rate. Types of theradical initiator may include an acetophenone-based photopolymerizationinitiator, a benzoin ether-based photopolymerization initiator, abenzophenone-based photopolymerization initiator, a thioxanthone-basedphotopolymerization initiator and the like, but are not limited thereto.As necessary, the radical curable composition may further includeadditional additives. Examples of the additive may include anantioxidant, an oligomer, an adhesion promotor and the like, but are notlimited thereto.

In one embodiment of the present specification, the radicalpolymerizable compound may be included in 80 parts by weight to 99.5parts by weight and the radical initiator may be included in 0.5 partsby weight to 20 parts by weight with respect to 100 parts by weight ofthe radical curable composition.

In one embodiment of the present specification, the radical curableadhesive component may use a radical polymerizable compound having aweight average molecular weight of 300 g/mol or greater so as to preventthe effects of radicals, which are generated while curing the radicalcurable composition, on the organic fluorescent substance.

The radical polymerizable compound having a weight average molecularweight of 300 g/mol or greater may be a monomer, a polymer, or a mixturethereof. By having a relatively large molecular weight, the radicalpolymerizable monomer or polymer having a weight average molecularweight of 300 g/mol or greater does not react with the organicfluorescent substance even when radicals are generated after UV curing,and optical properties of the color conversion film may not decline.Herein, it is the radical polymerizable compound that has a weightaverage molecular weight of 300 g/mol or greater, and other componentsnot affecting the properties of the organic fluorescent substance arenot limited in the weight average molecular weight.

According to one embodiment of the present specification, a protectivefilm may be further included on the phase transformation adhesive layer.

FIG. 1 illustrates a color conversion film according to one embodimentof the present specification. Specifically, FIG. 1 illustrates a colorconversion film in which a color conversion layer (20) is coated on asubstrate film (10), and a phase transformation adhesive layer (30) iscoated thereon.

In one embodiment of the present specification, the resin includes botha thermoplastic resin and a thermocurable resin, and although notparticularly limited in the type, poly(meth)acryl-based such aspolymethyl methacrylate (PMMA), polycarbonate-based (PC),polystyrene-based (PS), polyethylene-based, polyethylene glycol-based,polyarylene-based (PAR), polyurethane-based (TPU),styrene-acrylonitrile-based (SAN), polyvinylidene fluoride-based (PVDF),modified polyvinylidene fluoride-based (modified-PVDF) and the like maybe used.

In one embodiment of the present specification, the resin may exhibittransparent properties. Herein, being transparent means visible lighttransmittance being 75% or higher.

In one embodiment of the present specification, the solvent may bedimethylformamide, N,N-dimethylacetamide, pyridine, 2-methylpyridine,4-methylpyridine, butyl acetate, n-propyl acetate, ethyl acetate,xylene, toluene, cyclohexanone, methyl ethyl ketone, methyl isobutylketone or a combination thereof. More specifically, as the solvent, theabove-described solvents may be used either alone or as a mixture of twotypes.

In one embodiment of the present specification, the organic fluorescentdye absorbs light selected in a near-ultraviolet to visible region, anddyes emitting light having a different wavelength from the absorbinglight may be used.

In one embodiment of the present specification, the organic fluorescentdye includes any one or more of BODIPY-based, acridine-based,xanthene-based, arylmethane-based, coumarin-based, polycyclic aromatichydrocarbon-based, polycyclic hetero aromatic-based, perylene-based,pyrrole-based and pyrene-based derivatives. Specifically, the organicfluorescent dye includes one or two types of the above-describedmaterials. More specifically, the organic fluorescent dye uses aBODIPY-based organic fluorescent dye.

In one embodiment of the present specification, the organic fluorescentdye has a molecular absorption coefficient of 50,000 M⁻¹cm⁻¹ to 150,000M⁻¹cm⁻¹.

In one embodiment of the present specification, the substrate film mayhave a thickness of 1 μm to 100 μm. More specifically, the thickness maybe from 10 μm to 90 μm, and preferably from 20 μm to 80 μm.

In one embodiment of the present specification, the organic fluorescentdye is present in a form dispersed into the resin.

The content of the organic fluorescent dye is from 0.005 parts by weightto 2 parts by weight based on 100 parts by weight of the resin.

In one embodiment of the present specification, the color conversionfilm according to the embodiments described above additionally includeslight diffusing particles. By dispersing light diffusing particles intothe color conversion film instead of a light diffusing film having beenused in the art to enhance brightness, higher brightness may be obtainedcompared to using a separate light diffusing film, and an adheringprocess may be skipped as well.

As the light diffusing particles, particles having a high refractiveindex than the resin may be used, and examples thereof may include airor other gases, air- or gas-filled hollow beads or particles (forexample, air/gas-filled glass or polymers) including TiO₂, silica,borosilicate, alumina, or sapphire; polymer particles includingpolystyrene, polycarbonate, polymethyl methacrylate, acryl, methylmethacrylate, styrene, melamine resin, formaldehyde resin, or melamineand formaldehyde resins; or combinations thereof.

The light diffusing particles may have a particle diameter in a range of0.1 μm to 5 μm. The content of the light diffusing particles may bedetermined as necessary, and for example, may be from approximately 1parts by weight to 30 parts by weight with respect to 100 parts byweight of the resin solid content.

In one embodiment of the present specification, the color conversionfilm has a thickness of 2 μm to 200 μm.

In one embodiment of the present specification, the color conversionfilm may exhibit high brightness even with a small thickness of 2 μm to20 μm. This is due to the fact that the content of the fluorescentsubstance molecules included in the unit volume is higher than thecontent of quantum dots. For example, a color conversion film having a 5pm thickness using an organic fluorescent dye content of 0.5 wt % withrespect to the resin solid content may exhibit high brightness of 4000nit or greater based on the brightness of 600 nit of a blue backlightunit (blue BLU).

In one embodiment of the present specification, the color conversionfilm includes a substrate film; and a color conversion layer provided onthe substrate film.

In one embodiment of the present specification, the substrate film mayfunction as a support when preparing the color conversion film. Thesubstrate film is not limited in the type or thickness as long as it istransparent and capable of functioning as a support, and those known inthe art may be used. Herein, being transparent means visible lighttransmittance being 70% or higher. For example, a PET film may be usedas the substrate film.

As necessary, the substrate film may be replaced by a barrier film, or abather film may be provided on one surface or both surfaces of thesubstrate film.

The barrier film is not particularly limited as long as it is capable ofblocking moisture or oxygen, and those known in the art may be used. Forexample, the barrier film includes a bather layer having transmittanceof 10⁻¹ cc/m²/day for at least one of moisture and oxygen. For example,the bather layer may include aluminum oxides or nitrides, and ionicmetal oxides providing moisture or oxygen barrier properties. Thebarrier film may further include a buffer layer formed with one or moretypes selected from among sol-gel-based, acryl-based, epoxy-based andurethane-based coating solution compositions.

As one example, the barrier film may include an organic-inorganic hybridcoating layer, an inorganic material layer, and a protective coatinglayer including inorganic nanoparticles of which surfaces are modifiedwith organosilane provided on one surface or both surfaces of thesubstrate film. Herein, the inorganic material layer may be formed withmetal oxides or nitrides. The inorganic nanoparticles may benanoparticles of alumina, silica, zinc oxide, antimony oxide, titaniumoxide or zirconium oxide. The organic-inorganic hybrid coating layer maybe formed by curing an organosilane-including coating composition in asol state by heat or UV, and the coating solution composition in a solstate may include proper additive, solvent, polymerization catalyst andthe like together with organosilane.

In one embodiment of the present specification, an adhesive or gluinglayer may be provided on one surface of the color conversion film.Specifically, an adhesive or gluing layer may be provided on one surfaceof the color conversion layer not provided with the substrate film. Ascomponents forming the adhesive or gluing layer, those used in the artmay be used without limit.

Another embodiment of the present specification provides a method forpreparing a color conversion film, the method including preparing asubstrate film; forming a color conversion layer on the substrate film;and forming a phase transformation adhesive layer including an adhesiveresin matrix and a phase change material on the color conversion layer,wherein the phase change material is at least one selected from thegroup consisting of an organic monomer, a polymer and an inorganic salthydrate.

In one embodiment of the present specification, the forming of a colorconversion layer may include preparing a resin solution in which aresin, a solvent and an organic fluorescent dye are mixed; forming acolor conversion layer by coating the resin solution on the substratefilm; and drying the color conversion layer coated on the substratefilm.

In one embodiment of the present specification, the forming of a phasetransformation adhesive layer may include forming a phase transformationadhesive layer by coating a phase change solution including an adhesiveresin matrix, a solvent and a phase change material on the colorconversion layer; and thermally curing or photocuring the phasetransformation adhesive layer.

One embodiment of the present specification provides a method forpreparing a color conversion film, the method including preparing asubstrate film; preparing a resin solution in which a resin, a solventand an organic fluorescent dye are mixed; forming a color conversionlayer by coating the resin solution on the substrate film; drying thecolor conversion layer coated on the substrate film; forming a phasetransformation adhesive layer by coating a phase change solutionincluding an adhesive resin matrix, a solvent and a phase changematerial on the dried color conversion layer; and thermally curing orphotocuring the phase transformation adhesive layer.

In one embodiment of the present specification, the preparing of asubstrate film may be preparing a substrate film through extrusion orcoating, or preparing by purchasing a commercially-to availablesubstrate film

In the resin solution, the above-described organic fluorescent dye isdissolved, and therefore, the organic fluorescent dye is homogeneouslydistributed in the solution. This is different from a quantum dot filmpreparation process requiring a separate dispersion process.

In one embodiment of the present specification, the organic fluorescentdye-dissolved resin solution is not particularly limited in thepreparation method as long as the organic fluorescent dye and the resindescribed above are dissolved in the solution.

According to one example, the organic fluorescent dye-dissolved resinsolution may be prepared using a method of preparing a first solution bydissolving an organic fluorescent dye in a solvent, preparing a secondsolution by dissolving a resin in a solvent, and mixing the firstsolution and the second solution. When mixing the first solution and thesecond solution, it is preferred that these be homogeneously mixed.However, the method is not limited thereto, and a method ofsimultaneously adding and dissolving an organic fluorescent dye and aresin in a solvent, a method of dissolving an organic fluorescent dye ina solvent and subsequently adding and dissolving a resin, a method ofdissolving a resin in a solvent and then subsequently adding anddissolving an organic fluorescent dye, and the like, may be used.

The organic fluorescent dye included in the solution is the same asdescribed above. In one embodiment of the present specification, insteadof the resin included in the resin included in the solution, a monomercurable by a thermoplastic resin; or a mixture of a thermoplastic resinand a monomer curable by a thermoplastic resin. For example, the monomercurable by a thermoplastic resin includes a (meth)acryl-based monomer,and this may be formed as a resin matrix material by UV curing Whenusing such a curable monomer, an initiator required for curing may befurther added as necessary.

When using the first solution and the second solution, solvents includedin each of these solutions may be the same as or different from eachother. Even when different types of solvents are used in the firstsolution and the second solution, these solvents preferably havecompatibility so as to be mixed with each other.

Types of the solvent included in the solution are the same as above.

In one embodiment of the present specification, when using the monomercurable by a thermoplastic resin as the resin included in the solution,curing, for example, UV curing may be to conducted before the drying orat the same time as the drying.

When filming an organic fluorescent dye by extruding with a resin,extrusion methods known in the art may be used, and for example, thecolor conversion layer may be prepared by extruding the organicfluorescent dye with a resin such as polycarbonate-based (PC),poly(meth)acryl-based or styrene-acrylonitrile-based (SAN).

In one embodiment of the present specification, an adhesive or gluinglayer may be formed on the color conversion layer prepared as above. Theadhesive or gluing layer may be formed by coating a composition forforming an adhesive or gluing layer, and then polymerizing or curing theresult, or may also be formed by attaching an adhesive or gluing sheeton the color conversion layer. The adhesive or gluing sheet may bepolymerized or cured after being attached to the color conversion layer,but may also be polymerized or cured before the attachment as necessary.As the curing, UV curing may be used. The curing condition may bedetermined depending on the components and the composition ratio of thecomposition.

In the present specification, the “curing” means a process of beingconverted to a state capable of obtaining adhesion by a chemical orphysical action or reaction of components included in the phasetransformation adhesive layer by being exposed to heat and/or light. Forexample, the phase transformation adhesive layer is present in a liquidstate before curing, and may be converted to a solid state after curing.

In one embodiment of the present specification, the light diffusingparticles may be dispersed into the adhesive or gluing layer bydispersing the light diffusing particles to the composition for formingan adhesive or gluing layer. Herein, the light diffusing particles maybe directly dispersed to the composition for forming an adhesive orgluing layer, or a dispersion solution in which the light diffusingparticles are dispersed to a separate solvent may be mixed with thecomposition for forming an adhesive or gluing layer to increase a degreeof dispersion of the light diffusing particles. As necessary, asonicator or a shaker may be used to disperse the light diffusingparticles into a solvent

Another embodiment of the present specification provides a backlightunit including the color conversion film described above. The backlightunit may have backlight unit constitutions known in the art except forincluding the color conversion film.

FIG. 2 and FIG. 3 illustrate structures of the backlight unit accordingto one embodiment of the present specification. According to FIG. 2, thecolor conversion film according to the embodiments described above isprovided between a light guide plate and a reflecting plate. Accordingto FIG. 3, the color conversion film according to the embodimentsdescribed above is provided on a surface opposite to a surface facing areflecting plate of a light guide plate. FIGS. 2 and 3 illustrate aconstitution including a light source and a reflecting plate surroundingthe light source, however, the constitution is not limited to such astructure, and may vary depending on the backlight unit structure knownin the art. In addition, as the light source, a direct type as well as aside chain type may be used, and the reflecting plate or the reflectivelayer may not be included or may be replaced with other constituents asnecessary.

Another embodiment of the present specification provides a displayapparatus including the backlight unit described above. For example, thedisplay apparatus includes a display module and a backlight unit FIG. 4illustrates a structure of the display apparatus according to oneembodiment of the present specification. According to FIG. 4, the colorconversion film according to the embodiments described above is providedon a surface opposite to a surface facing a reflecting plate of a lightguide plate, and a display module is provided on the top of the colorconversion film. However, the structure of the display apparatus is notlimited thereto, and the structure is not particularly limited as longas it includes the backlight unit described above as a constituent Asnecessary, additional films such as a light diffusing film, a lightconcentrating film and a brightness enhancing film may be furtherprovided between the display module and the backlight unit.

The display apparatus is not particularly limited, and may be, forexample, a TV, a computer monitor, a laptop, a mobile phone and thelike.

Hereinafter, the present specification will be described in detail withreference to examples. However, the examples according to the presentspecification may be modified to various other forms, and the scope ofthe present application is not to be construed as being limited to theexamples described below. Examples of the present specification areprovided in order to more fully describe the present specification tothose having average knowledge in the art.

EXAMPLE 1

A first solution was prepared by dissolving an acrylate-based adhesivein a xylene solvent, and adding a curing initiator thereto. A phasechange material (poly(ethylene glycol), PEG) was dissolved in a xylenesolvent to prepare a second solution. An adhesive solution was preparedby homogeneously mixing the first solution and the second solution sothat, with respect to 100 parts by weight of the acrylate-basedadhesive, the content of the phase change material was 70 parts byweight. This adhesive to solution was coated on a protective film, andthermally cured to prepare a phase transformation adhesive layer.

A green fluorescent substance and a red fluorescent substance of thefollowing structural formulae were dissolved in a molar ratio of 50:1 ina xylene solvent to prepare a third solution.

A thermoplastic resin (PMMA) was dissolved in a xylene solvent toprepare a fourth solution. The third solution and the fourth solutionwere homogeneously mixed so that, with respect to 100 parts by weight ofthe thermoplastic resin, the content of the green and red fluorescentsubstances was 0.45 parts by weight, and the content of TiO₂ particleswas 10 parts by weight. This solution was coated on a PET substrate, andthen dried to prepare a color conversion layer. Herein, the TiO₂particles may be added and mixed to any one of the third and the fourthsolutions, or a fifth solution including the TiO₂ particles may beprepared, or the TiO₂ particles may be introduced when mixing the thirdand the fourth solutions.

The phase transformation adhesive layer was laminated on the colorconversion layer side to prepare a color conversion film.

EXAMPLE 2

A color conversion film was prepared in the same manner as in Example 1except that, as the phase change material, a microcapsule phase changematerial (Mild Riken Industrial Co., Ltd., PMCD-32SP) was used so thatthe content was 70 parts by weight with respect to 100 parts by weightof the acrylate-based adhesive.

Comparative Example 1

An adhesive solution was prepared by dissolving 17 parts by weight of anacrylate-based adhesive in xylene, and adding a curing initiatorthereto. This adhesive solution was coated on a protective film, andthermally cured to prepare an adhesive layer.

A first solution was prepared by dissolving the same green and redfluorescent substances as in Example 1 in a xylene solvent in a molarratio of 50:1.

A thermoplastic resin (PMMA) was dissolved in a xylene solvent toprepare a second solution. A powder-type phase change material(poly(ethylene glycol), PEG) was dissolved in a xylene solvent toprepare a third solution. The first solution, the second solution andthe third solution were homogeneously mixed so that, with respect to 100parts by weight of the thermoplastic resin, the content of the green andred fluorescent substances was 0.45 parts by weight, the content of thephase change material was 70 parts by weight, and the content of TiO₂particles was 10 parts by weight. This solution was coated on a PETsubstrate, and then dried to prepare a color conversion layer. Herein,the TiO₂ particles may be added and mixed to any one of the first to thethird solutions, or a fourth solution including the TiO₂ particles maybe prepared, or the TiO₂ particles may be introduced when mixing thefirst to the third solutions.

The adhesive layer was laminated on the color conversion layer side toprepare a color conversion film.

Comparative Example 2

A color conversion film without using a phase change material wasprepared in the same manner as in Example 1 except that the phase changematerial was not used. Light emission spectrum of each of the colorconversion films prepared according to Example 1 and Comparative Example2 was measured using a spectroradiometer (SR series of TOPCONCorporation). Specifically, the prepared color conversion film waslaminated on one surface of a light guide plate of a backlight unitincluding an LED blue backlight (maximum light emission wavelength 450nm) and the light guide plate, and after laminating a prism sheet and aDBEF film on the color conversion film, a brightness spectrum of thefilm was measured, and the results are shown in FIG. 5. In addition,results of measuring brightness and quantum efficiency (QY) of each ofthe color conversion films are shown in the following Table 1. Accordingto FIG. 5 and Table 1, it was identified that optical properties did notdecline much even when introducing the phase change material to thecolor conversion film.

TABLE 1 Comparative Example 2 Example 1 Relative brightness 100% 86.4%Quantum Efficiency 0.95 0.81

For each of the color conversion films prepared according to theexamples and the comparative examples, repeated driving durability wasevaluated. Specifically, the prepared color conversion film waslaminated on one surface of a light guide plate of a backlight unitincluding an LED blue backlight (maximum light emission wavelength 450nm) and the light guide plate, and a prism sheet, a DBEF film and areflecting plate were laminated on the color conversion film. In orderto simulate a situation of heat generation caused by display driving,the laminated structure was placed on a hot plate and heated to 60° C.,and a cycle of driving the backlight for 24 hours, cooling to roomtemperature for 24 hours and blocking the backlight was repeated 10times. After each cycle, light emission spectrum of the color conversionfilm was measured using a spectroradiometer to analyze changes in theoptical properties, and the results are shown in FIG. 6 and Table 2. Inthe color conversion film prepared according to Comparative Example 1,the phase change material was liquefied and flowed out of the colorconversion film during the first driving, and further driving durabilityevaluation was not able to be progressed, whereas the color conversionfilm prepared according to Example 1 exhibited enhanced durabilitywithout separate leakages despite the high phase change materialcontent.

TABLE 2 Optical properties after 10 Brightness % Compared Times ofRepeated Driving to Initial Brightness Example 1 99.8% Example 2 98.0%Comparative Example 1 — Comparative Example 2 93.5%

1. A color conversion film comprising: a substrate film; a colorconversion layer provided on the substrate film; and a phasetransformation adhesive layer provided on the color conversion layer,wherein the phase transformation adhesive layer includes an adhesiveresin matrix and a phase change material; and the phase change materialis at least one material selected from an organic monomer, a polymer andan inorganic salt hydrate.
 2. The color conversion film of claim 1,wherein the phase change material has a solid-liquid phase transitionoccurring at 30° C. to 80° C.
 3. The color conversion film of claim 1,wherein a content of the phase change material is from 10 parts byweight to 80 parts by weight with respect to 100 parts by weight of thephase transformation adhesive layer.
 4. The color conversion film ofclaim 1, wherein the phase change material has a microcapsule structurehaving a shell and a core.
 5. The color conversion film of claim 4,wherein the shell is at least one material selected from anurea-formaldehyde, a melamine-formaldehyde, a polyurethane resin, apolyurea resin, an epoxy resin, a gelatin and a polyacrylic resin; andthe core is at least one material selected from an organic monomer, apolymer and an inorganic salt hydrate.
 6. The color conversion film ofclaim 1, wherein the organic monomer is at least one compound selectedfrom a paraffin-based compound, a fatty acid-based compound, analcohol-based compound and a carbonate-based compound.
 7. The colorconversion film of claim 1, wherein the polymer is at least one selectedfrom poly(ethylene glycol), poly(propylene oxide (PPO) andpolytetrahydrofuran (PTHF).
 8. The color conversion film of claim 1,wherein the inorganic salt hydrate is at least one material selectedfrom LiNO₃.3H₂O, Na₂SO₄.10H₂O, NaCH₃COO.3H₂O, CaBr₂.6H₂O, Na₂HPO₄.12H₂O,Zn(NO₃)₂.nH₂O, Na₂S₂O₃.5H₂O and Cd(NO₃)₂.4H₂O.
 9. The color conversionfilm of claim 1, wherein the adhesive resin matrix is a cationpolymerizable adhesive component, a radical curable adhesive component,or a mixture thereof.
 10. The color conversion film of claim 1, furthercomprising a protective film on the phase transformation adhesive layer.11. The color conversion film of claim 1, wherein the color conversionlayer includes an organic fluorescent dye, and the organic fluorescentdye includes any one or more of BODIPY-based, acridine-based,xanthene-based, arylmethane-based, coumarin-based, polycyclic aromatichydrocarbon-based, polycyclic hetero aromatic-based, perylene-based,pyrrole-based and pyrene-based derivatives.
 12. A method for preparing acolor conversion film, the method comprising: providing a substratefilm; forming a color conversion layer on the substrate film; andforming a phase transformation adhesive layer including an adhesiveresin matrix and a phase change material on the color conversion layer,wherein the phase change material is at least one material selected froman organic monomer, a polymer and an inorganic salt hydrate.
 13. Themethod for preparing a color conversion film of claim 12, wherein theforming of a color conversion layer includes, mixing a resin, a solventand an organic fluorescent dye to prepare a resin solution; coating theresin solution on the substrate film to form a color conversion layer;and drying the color conversion layer coated on the substrate film. 14.The method for preparing a color conversion film of claim 12, whereinthe forming of a phase transformation adhesive layer includes, coating aphase change solution including an adhesive resin matrix, a solvent anda phase change material on the color conversion layer; and thermallycuring or photocuring the phase transformation adhesive layer to formthe phase transformation adhesive layer.
 15. A backlight unit comprisingthe color conversion film of claim
 1. 16. A display apparatus comprisingthe backlight unit of claim 15.